i have been trying for months to get a display working with a UNO ,both 2 line and 4 line sparkfun LCDs wit the common chip on board.it lights up but theres nothing to see on the display .ive used sample progs from tronixstuff and UNO examples and arduino cookbook examples but nothing works as it should .it should be easy with pins 4 5 6 7 8 9 connected and some V and grnd but no figures on display .no scrolling no nothing .i have a 10k trim pot to adjust the display but just no display figures .help

There have been dozens (it seems like hundreds) of posts similar to yours in this forum over the past few years. It would only take a cursory look at them to see that we cannot help you unless you post the exact code that you used along with a clear photograph of your connections.

i have been trying for months to get a display working with a UNO ,both 2 line and 4 line sparkfun LCDs wit the common chip on board.it lights up but theres nothing to see on the display .ive used sample progs from tronixstuff and UNO examples and arduino cookbook examples but nothing works as it should .it should be easy with pins 4 5 6 7 8 9 connected and some V and grnd but no figures on display .no scrolling no nothing .i have a 10k trim pot to adjust the display but just no display figures .help

progs upload but theres nothing on display its barren

This is probably all about the pins. The sample from tronixstuff is probably the kiss of death unless you are using their shield, which I believe is unique. I assume you are not using their shield. I have a cheapo eBay shield on a tronixstuff EtherTen, and fell into the same trap. I had the first success with code from

i got some basic blocks on the display using pins 12 11, 5 4 3 2 as the example in the arduino cookbook ,contrast works ok but no symbols dancing across the blocks ...no hello world example or scroll ...

I just dug out the code I used when I tested my LCD a while ago. It's based on Mike Bramwell's code- I can't remember where that came from. It has this line, which I don't pretend to understand. I just used it as is and it worked...

I assume the order of those pin numbers is important. I see from your post, @knuckles, that you mention pins 4, 5, 6, 7, 8, 9 and wonder if you've got them coded in the order 4, 5, 6, 7, 8, 9 whereas it should maybe be 8, 9, 4, 5, 6, 7?

It has this line, which I don't pretend to understand. I just used it as is and it worked...

Well this is fully explained but very carefully hidden on the Arduino site.

Start here: http://arduino.cc/en/Tutorial/LiquidCrystalScroll down to the bottomUse the Liquid Crystal Library link to get here: http://arduino.cc/en/Reference/LiquidCrystalUse the LiquidCrystal() link to get here: http://arduino.cc/en/Reference/LiquidCrystalConstructorAnd there it is under 'Syntax'